Chronic fatigue syndrome (CFS) is a complicated disorder characterized by extreme fatigue that can't be explained by any underlying medical condition. The fatigue may worsen with physical or mental activity, but doesn't improve with rest.

Chronic fatigue syndrome has also been called myalgic encephalomyelitis (ME) and, more recently, systemic exertion intolerance disease (SEID). Although CFS/ME and SEID share the same major symptom of chronic fatigue, there is variation between the definitions of these disorders. The symptom of chronic fatigue also may arise from more than one underlying condition.

The cause of chronic fatigue syndrome is unknown, although there are many theories — ranging from viral infections to psychological stress. Some experts believe chronic fatigue syndrome might be triggered by a combination of factors.

There's no single test to confirm a diagnosis of chronic fatigue syndrome. You may need a variety of medical tests to rule out other health problems that have similar symptoms. Treatment for chronic fatigue syndrome focuses on symptom relief.

Chronic fatigue syndrome has eight official signs and symptoms, plus the central symptom that gives the condition its name:

Fatigue

Loss of memory or concentration

Sore throat

Enlarged lymph nodes in your neck or armpits

Unexplained muscle pain

Pain that moves from one joint to another without swelling or redness

Headache of a new type, pattern or severity

Unrefreshing sleep

Extreme exhaustion lasting more than 24 hours after physical or mental exercise

When to see a doctor

Fatigue can be a symptom of many illnesses, such as infections or psychological disorders. In general, see your doctor if you have persistent or excessive fatigue.

Scientists don't know exactly what causes chronic fatigue syndrome. It may be a combination of factors that affect people who were born with a predisposition for the disorder.

Some of the factors that have been studied include:

Viral infections. Because some people develop chronic fatigue syndrome after having a viral infection, researchers question whether some viruses might trigger the disorder.

Immune system problems. The immune systems of people who have chronic fatigue syndrome appear to be impaired slightly, but it's unclear if this impairment is enough to actually cause the disorder.

Hormonal imbalances. People who have chronic fatigue syndrome also sometimes experience abnormal blood levels of hormones produced in the hypothalamus, pituitary glands or adrenal glands. But the significance of these abnormalities is still unknown.

Age. Chronic fatigue syndrome can occur at any age, but it most commonly affects people in their 40s and 50s.

Sex. Women are diagnosed with chronic fatigue syndrome much more often than men, but it may be that women are simply more likely to report their symptoms to a doctor.

Stress. Difficulty managing stress may contribute to the development of chronic fatigue syndrome.

Possible complications of chronic fatigue syndrome include:

Depression

Social isolation

Lifestyle restrictions

Increased work absences

If you have signs and symptoms of chronic fatigue syndrome, you're likely to start by seeing your family doctor or a general practitioner. It can be difficult to absorb all the information provided during an appointment, so you might want to arrange for a friend or family member to accompany you. Having someone else hear the information can help you later in case there's something you missed or forgot.

What you can do

Before your appointment, you may want to write a list that includes:

Your signs and symptoms. Be thorough. While fatigue may be affecting you most, other symptoms — such as memory problems or headache — are also important to share with your doctor.

Key personal information. Recent changes or major stressors in your life can play a very real role in your physical well-being.

Health information. List any other conditions for which you're being treated and the names of any medications, vitamins or supplements you take regularly.

Questions to ask your doctor. Creating your list of questions in advance can help you make the most of your time with your doctor.

If these tests don't pinpoint the cause of my symptoms, what additional tests might I need?

On what basis would you make a diagnosis of chronic fatigue syndrome?

Are there any treatments or lifestyle changes that could help my symptoms now?

Do you have any printed materials I can take with me? What websites do you recommend?

What activity level should I aim for while we're seeking a diagnosis?

Do you recommend that I also see a mental health provider?

Don't hesitate to ask other questions during your appointment as they occur to you.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, such as:

What are your symptoms and when did they begin?

Does anything make your symptoms better or worse?

Do you have problems with memory or concentration?

Are you having trouble sleeping?

How often do you feel depressed or anxious?

How much do your symptoms limit your ability to function? For example, have you ever had to miss school or work because of your symptoms?

What treatments have you tried so far for this condition? How have they worked?

There's no single test to confirm a diagnosis of chronic fatigue syndrome. Because the symptoms of chronic fatigue syndrome can mimic so many other health problems, you may need patience while waiting for a diagnosis.

Your doctor must rule out a number of other illnesses before diagnosing chronic fatigue syndrome. These may include:

Sleep disorders. Chronic fatigue can be caused by sleep disorders. A sleep study can determine if your rest is being disturbed by disorders such as obstructive sleep apnea, restless legs syndrome or insomnia.

Medical problems. Fatigue is a common symptom in several medical conditions, such as anemia, diabetes and underactive thyroid (hypothyroidism). Lab tests can check your blood for evidence of some of the top suspects.

Mental health issues. Fatigue is also a symptom of a variety of mental health problems, such as depression, anxiety, bipolar disorder and schizophrenia. A counselor can help determine if one of these problems is causing your fatigue.

Diagnostic criteria

To meet the diagnostic criteria of chronic fatigue syndrome, or myalgic encephalomyelitis, you must have unexplained, persistent fatigue for six months or more, along with at least four of the following signs and symptoms:

Loss of memory or concentration

Sore throat

Enlarged lymph nodes in your neck or armpits

Unexplained muscle pain

Pain that moves from one joint to another without swelling or redness

Headache of a new type, pattern or severity

Unrefreshing sleep

Extreme exhaustion lasting more than 24 hours after physical or mental exercise

In contrast, for a diagnosis of systemic exertion intolerance disease (SEID), you must have the following three symptoms:

Unexplained, persistent fatigue

Extreme exhaustion lasting more than 24 hours after physical or mental exercise

Unrefreshing sleep

And at least one of these two symptoms:

Cognitive impairment

Dizziness and lightheadedness

Chronic fatigue accompanies many medical conditions and may not be an isolated symptom. In such cases, the better term may be "chronic multifactorial fatigue."

Because chronic fatigue syndrome affects people in many different ways, your treatment will be tailored to your specific set of symptoms. Symptom relief may include certain medications:

Antidepressants. Many people who have chronic fatigue syndrome are also depressed. Treating your depression can make it easier for you to cope with the problems associated with chronic fatigue syndrome. Low doses of some antidepressants also can help improve sleep and relieve pain.

Sleeping pills. If home measures, such as avoiding caffeine, don't help you get better rest at night, your doctor might suggest trying prescription sleep aids.

Therapy

There's no known cure for chronic fatigue syndrome, and the most effective treatment for chronic fatigue syndrome remains uncertain. However, there's evidence that a multipronged approach may be helpful:

Pace yourself. Keep your activity on an even level. If you do too much on your good days, you may have more bad days.

Graded exercise. In order to improve daily function, more than pacing alone is needed. Previous studies suggest that graded exercise is an effective and safe treatment, but evidence for this remains limited.

A physical therapist can help determine what types of exercise are best for you. Inactive people often begin with range-of-motion and stretching exercises for just a few minutes a day. Slow, incremental increases in activity then take place over weeks to months.

If you're exhausted the next day, you're doing too much. Your strength and endurance will improve as you gradually increase the intensity of your exercise over time.

Psychological counseling. Talking with a counselor can help you figure out options to work around some of the limitations that chronic fatigue syndrome imposes on you. Feeling more in control of your life can improve your outlook dramatically. Cognitive behavioral therapy and self-management strategies are among the most helpful.

Not everyone who has severe chronic fatigue and postexertional malaise — intense exhaustion or mental fatigue after physical or mental activities that were once tolerated — responds to treatment in the same way. People who have a better chance of treatment success tend to have less impairment, focus less on symptoms, comply with counseling programs and pace themselves to avoid overexertion and underexertion.

For chronic fatigue syndrome, certain self-care measures may help:

Reduce stress. Develop a plan to avoid or limit overexertion and emotional stress. Allow yourself time each day to relax. That may mean learning how to say no without guilt.

Improve sleep habits. Go to bed and get up at the same time each day. Limit daytime napping and avoid caffeine, alcohol and nicotine.

Pace yourself. Keep your activity on an even level. If you do too much on your good days, you may have more bad days.

Many alternative therapies have been promoted for chronic fatigue syndrome. It's difficult to determine whether these therapies actually work, partly because the symptoms of chronic fatigue syndrome often are linked to mood and can vary from day to day.

Pain associated with chronic fatigue syndrome may be helped by:

Acupuncture

Massage

Yoga or tai chi

The experience of chronic fatigue syndrome varies from person to person. For many people, however, the symptoms are more bothersome early in the course of the illness and then gradually decrease. Emotional support and counseling may help you and your loved ones deal with the uncertainties and restrictions of chronic fatigue syndrome.

You may find it therapeutic to join a support group and meet other people with chronic fatigue syndrome. Support groups aren't for everyone, and you may find that a support group adds to your stress rather than relieves it. Experiment and use your own judgment to determine what's best for you.

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